1. Field of the Invention
This invention relates to a security bolt system for cabinets.
2. Prior Art Statement
It is known to provide a lock having a closure member comprising a stationary stud having a threaded end, a sleeve surrounding the threaded end of the stud, a complementary member having an internal thread adapted to engage the stud and an external tapered surface adapted to engage the sleeve, the complementary member carried by one element of the enclosure and the stationary stud and sleeve carried by another element of the enclosure, the members adapted to maintain the elements in fixed relative position. For instance, see the U.S. Pat. No. 1,856,091 issued on 3 May 1932, to Augusto Dina. As with most closure locks using a bolt to capture one element against the other, the end of the bolt must be inserted into a threaded interior, the threads engaged and the bolt tightened thereinto. Often times, the end of the bolt is damaged from attempts to insert same into the threaded interior despite the fact that the end of the bolt is provided with a taper. With the mating tapered surfaces, the lock system of Dina is very expensive to manufacture. There is a need for a lock having a closure member that presents the bearing surfaces to a position behind a bolt head wherein the bolt is already retained in a threaded receiver where the mating parts may be extruded from metal or plastic material.
It is also known to provide a lock assembly for a refrigerated cabinet has a spring loaded bolt carried by the door and a fixed nut in the cabinet wherein the bolt is inserted into the nut, the threads engaged and the bolt tightened into the nut to effect closure of the refrigerated cabinet. Later refrigerated cabinets have a split nut that parts when the bolt is inserted into the split nut. For instance, see the U.S. Pat. No. 3,089,330 issued on 7 Dec. 1961 to William J. Kerr. Damage to the end of the bolt still exists as the threads are jammed into initial engagement with the nut. Thus, there is a need for threaded security bolt system wherein the threads of the bolt are always in engagement with the nut and the closure parts are positioned behind the head of the bolt upon closure of a door against the cabinet.
It is further known to provide an overhang on a movable closure member that substantially conceals a closure bolt and a locking device which obstructs access to the head of the closure bolt. Access to the bolt is provided through a hole in the overhang after removal of the locking device. The closure bolt is carried by the movable closure lid but must be inserted into the threaded nut and the threads engaged before the closure lid is drawn against the inside surface of a cubic receptacle formed under the overhanging portion. For instance, see U.S. Pat. No. 3,784,727 issued on 8 Jan. 1974 to Harold Dennis Haubein. It is readily apparent that the end of the bolt is subject to damage when inserted first through a hole in the cabinet wall and thereafter into the nut. A simpler, more cost effective closure device is dictated by the prior art, specifically a closure device that has the threads of the bolt always captured in the nut wherein a bearing surface of the parts of the enclosure are arranged behind the head of the bolt.
A locking mechanism for a transformer enclosure door is described in U.S. Pat. No. 6,106,035 issued on 22 Aug. 2000 to David L. Hetherington that has a spring biased bolt carried by one part of the enclosure and a wave spring nut carried in another part of the enclosure. The nose end of the bolt must still be inserted into the threaded wave spring in a ratcheting manner and then tightened in the manner described in Haubein above. The mechanism of Hetherington is expensive to manufacture and subject to damage when used repeatedly. Accordingly, there is still a need for a simpler, more cost effective closure device that has the threads of the bolt always captured in the nut wherein a bearing surface of the parts of the enclosure are arranged behind the head of the bolt to ensure repeated usage.
Finally, it is known to provide a conventional lock mechanism on one side of the housing which comprises a conventional type cooperating hasp and receptacle members. The members include a threaded socket for a “Penta-Bolt” and may include cooperating holes for receiving a padlock. The hasp member is rotatable and, upon closure of the removable portion of the housing to the bottom part, is inserted into a slot behind the threaded cylindrical socket. The bolt is then inserted into the threaded socket and driven into the a hole in the hasp member and a hole in the removable portion. For instance, see the U.S. Pat. No. 4,365,108 issued on 21 Dec. 1982 to William L. Bright. The bolt only projects into a hole in the hasp and into a hole in the cabinet so there is no threaded connection of the removable portion to the fixed portion of the cabinet. The bearing surface for the bolt is the bottom of the cylindrical socket provided only on the removable portion of the cabinet. Thus there is a need for a closure lock that carries the locking bolt in a threaded socket and has a portion of the bearing surface for the locking bolt in both enclosure members of the cabinet.